Magnetic resonance molecular imaging strategies have been explored by specifically targeting oncogenes such as HER-2 (c-erbB-2, Neu), bcl-2/bcl-xL, protein kinase A, and the transferrin receptor gene. The human transferrin receptor (hTfR) has been used as a molecular target to direct therapeutic agents to tumor cells and to shuttle drugs across the blood-brain barrier. Expression and regulation of hTfR'receptors can be visualized by NMR imaging by studying the receptors with a sterically protecting iron-containing magnetic hTfR probe. A cationic immunoliposome system which covalently conjugates the single-chain antibody variable region fragment (scFv) against the hTfR has been used to improve p53 tumor suppressor gene therapy employed in the human breast cancer metastasis model. This scFv-immunolipdsome can systematically deliver the complexed gene to tumors in vivo. In comparison to a whole antibody or transferrin molecule, scFv has a much smaller size, enabling it to penetrate more easily through solid tumors. In this study, we will utilize the TfR scFv-immunoliposome along with MR contrast agents to improve contrast agent-tumor affinity and specificity. This will enhance MR diagnostic imaging capabilities, particularly those needed for early detection.